Nordic Pure 12 x 12 x 1/2 MERV 13 rated flat panel AC air filters consist of an internal frame bonded between flat layers of two different types of electrostatically charged filter media. The first layer is a polyester filter media which acts as a pre-filter, capturing larger airborne particulates. The second layer is a MERV rated smooth poly blend filter material which attracts and captures smaller particulates. MERV 13 1/2” filters will attract and capture dust, pollen, mold spores, droplets from sneezes and coughs and tobacco and fireplace smoke. 1/2" filters are great for apartments, window units, campers, RVs, and any air system that requires half inch air filters.